Is the plot really going to concern Shepard saving Earth? How is (s)he going to send in the cavalry if the Reapers for instance blow up the Charon mass relay, cutting off Earth from the rest of the galaxy?
Not to mention, if the game really begins with the invasion of Earth, there'll have to be a very good excuse to spend X amount of time scraping together allies, shooting mercs on uncharted planets and convincing Kaidan/Ashley to a m